Bryophytes 2: Anthocerotophyta and Marchantiophyta
Summary
TLDREste vídeo ofrece una visión general de las briofitas, las primeras plantas terrestres, y se centra en dos linajes: Anthocerotophyta (briofitas cornudas) y Marchantiophyta (hepáticas). Se discute su posible monofilia o parafilia, y se explican sus características como la falta de tejido vascular lignificado, la necesidad de condiciones húmedas y la predominancia del gametofito. Además, se exploran las diferencias entre hornworts y liverworts, y se describen sus ciclos de vida y adaptaciones para la vida en tierra, como las asociaciones con hongos y bacterias para la captación de agua y fijo de nitrógeno.
Takeaways
- 🌿 Los briofitas son los primeros grupos de plantas que evolucionaron en la tierra y se creen que son parafílicas o posiblemente monofileticas.
- 🍃 Los briofitas carecen de tejido vascular lignificado, lo que les impide mantenerse erguidos y requiere condiciones húmedas para sobrevivir.
- 💧 A pesar de la falta de raíces, los briofitas se asocian con hongos y cianobacterias para obtener agua y nutrientes.
- 🌱 La mayoría de los briofitas no pueden sobrevivir en condiciones secas, aunque algunas especies de musgos pueden secarse y rehidratarse.
- 🌳 Los briofitas tienen predominio del gametofito, lo que significa que la parte haploida de su ciclo de vida es más grande y tiene una vida útil más larga.
- 🌱 Dawsonia superba es una excepción entre los musgos, creciendo hasta dos pies de altura y posee estructuras analógicas a los tejidos vasculares.
- 🌿 Los hornworts (Anthocerotophyta) son un grupo de briofitas con un tejido llamado tálamo que se asemeja a un reguero y contiene estructuras vase-like.
- 🌱 Los liverworts (Marchantiophyta) pueden ser confundidos con musgos, pero se pueden distinguir por la presencia de pequeñas hojas inferiores y por sus estructuras de reproducción.
- 🌱 Los liverworts producen estructuras llamadas gemmae, que son clones del gametofito y pueden crecer en un nuevo tálamo.
- 🌱 La vida de los liverworts se puede resumir en un ciclo que comienza con las esporas, se desarrollan en gametofitos y luego se fertilizan para formar un zigoto que crece en un esporófito.
Q & A
¿Cuáles son las dos lineas de briofitas que se discuten en el segundo video?
-En el segundo video se discuten las lineas de Anthocerotophyta, conocidas como las cuernoplantas, y Marchantiophyta, conocidas como las hongos de hígado.
¿Por qué se cambió el nombre de Hepatophyta a Marchantiophyta para las hongos de hígado?
-El nombre de Hepatophyta se cambió recientemente a Marchantiophyta, aunque el motivo exacto del cambio no se detalla en el guion.
¿Cómo se relacionan las briofitas con la evolución de las plantas terrestres?
-Las briofitas son consideradas el primer grupo de plantas que evolucionaron en la tierra, y su relación con la evolución de las plantas terrestres se debate en términos de si son monofileticas o parafileticas.
¿Qué características comparten las tres grandes lineas de briofitas mencionadas?
-Las tres grandes lineas de briofitas son pequeñas y prostradas, lo que significa que se extienden en la superficie en lugar de tener una estructura erguida, y carecen de tejido vascular lignificado.
¿Por qué las briofitas requieren condiciones húmedas para sobrevivir?
-Las briofitas requieren condiciones húmedas porque no tienen tejido vascular lignificado y dependen de la humedad para la absorción de agua y la fijación de nitrógeno.
¿Qué es la dominancia del gametofita en las briofitas y cómo se relaciona con el ciclo de vida de la planta?
-La dominancia del gametofita en las briofitas significa que la parte del ciclo de vida que es haploida y fotosintética es la más grande y tiene una vida útil más larga, lo que es una característica que las une.
¿Qué características hacen que Dawsonia superba sea excepcional entre las briofitas?
-Dawsonia superba es excepcional porque puede crecer hasta dos pies de altura y, aunque no tiene tejido vascular lignificado, tiene estructuras similares que le permiten transmitir agua y azúcares a través de su cuerpo.
¿Cómo se diferencian las cuernoplantas de otras briofitas en términos de su estructura?
-Las cuernoplantas se caracterizan por tener un tejido plano y raíces similares llamadas rizoides que sirven para anclaje en lugar de absorción de agua, y su esporófito crece desde un meristemo basal.
¿Qué es un rizoide en las briofitas y qué función cumple?
-Un rizoide es una estructura que se asemeja a una raíz en las briofitas, que sirve para anclar la planta al terreno en lugar de para la absorción de agua, ya que no contiene tejido vascular.
¿Qué适应性 de las briofitas se evidencia en la presencia de estomatas y cutícula en el esporófito y no en el gametofita?
-La presencia de estomatas y cutícula en el esporófito de las briofitas indica una adaptación al ambiente terrestre, lo que sugiere una evolución hacia la eficiencia en la regulación del intercambio de gases y la conservación de agua.
¿Cómo se reproducen las briofitas a nivel de las hongos de hígado y cómo se diferencia de la reproducción de otras plantas?
-Las hongos de hígado pueden reproducirse asexivamente a través de estructuras llamadas gemmae y tienen poros simples para el intercambio de gases, lo que difiere de la reproducción sexual que involucra la producción de esporos en el esporófito.
Outlines
🌿 Introducción a los briofitas
El vídeo comienza explicando que los briofitas fueron los primeros grupos de plantas que evolucionaron en la tierra y se discute si son parafilogéneticos o monofiléticos. Se menciona que los briofitas carecen de tejido vascular lignificado y requieren condiciones húmedas para sobrevivir. Además, se destaca que los briofitas tienen predominio de la gametofito, lo que significa que la parte fotosintética y haploide es la más grande y tiene una vida más larga que la parte diploide. También se menciona la excepción de los musgos que pueden sobrevivir en condiciones secas y su capacidad para secarse y rehidratarse. Finalmente, se menciona que los briofitas necesitan agua para reproducirse debido a que el esperma tiene que viajar por el agua para fertilizar los óvulos.
🌿 Los briofitas: hornerías y hepaticas
Se describen los hornerías y las hepaticas como dos de las tres grandes linajes de briofitas. Se menciona que los hornerías pueden no estar genéticamente cercanos a las plantas vasculares y podrían haber evolucionado primero. Se explica que las hornerías tienen una textura de tejido similar a un flap y tienen estructuras llamadas rizoides que sirven para anclarse al terreno. Además, se discute la relación de las hornerías con hongos y ciánobacterias, lo que les permite acceder a nutrientes en un entorno difícil. Se describe la estructura de las hornerías, incluyendo el gametofito y el esporófito, y se menciona que el esporófito de las hornerías crece desde un meristemo basal, lo que es inusual en la mayoría de las plantas. También se menciona que las hepaticas pueden tener dos tipos de cuerpos planos y se discuten sus características, como las gemmae y los poros simples para el intercambio de gases.
🌿 Hepáticas: características y ciclo de vida
Se describen las hepaticas con detalles sobre su apariencia, incluyendo las hojas superiores y las inferiores que son características para diferenciarlas de los musgos. Se menciona que las hepaticas producen rizoides a lo largo de su superficie y pueden producir esporófitos a lo largo del cuerpo o solo al final de las estructuras. Se explica la estructura del esporófito en las hepaticas, que se divide en dos partes principales: el seta (el tallo) y el esporangio (donde se producen los esporos). Se detalla el proceso de dehiscence, donde el esporangio se abre y libera los esporos. También se describe el ciclo de vida de las hepaticas, desde la producción de esporos a través de la meiosis, el desarrollo de gametofitos y la fertilización, y cómo el zygote se desarrolla en el gametofito femenino para formar un nuevo esporófito.
🌿 Detalles del ciclo de vida de las hepaticas
Se proporciona una descripción detallada de los componentes del ciclo de vida de las hepaticas, incluyendo la formación de gemmae y la diferenciación entre gametofitos masculinos y femeninos. Se describen las estructuras que portan los óvulos (arquigoniofiros) y los espermatofitos (antereidiofiros) y cómo se produce la fertilización. Se menciona el proceso de síngami, que es cuando la fusión del núcleo y la fertilización ocurren. También se discute cómo el zigoto se desarrolla en el gametofito femenino y cómo cada esporófito tiene un seta y un esporangio donde se producen los esporos por medio de la meiosis. Finalmente, se describe cómo los esporangios se abren para liberar los esporos y cómo esto puede parecer similar a los musgos, pero con diferencias clave en las hojas y los esporangios.
Mindmap
Keywords
💡Briófitas
💡Antocerotofitas
💡Marchantiofitas
💡Gameófito
💡Esporófito
💡Rizoides
💡Cianobacterias
💡Gemmae
💡Parafilético
💡Monofiletico
Highlights
Bryophytes are the first group of plants to evolve on land.
Bryophytes are likely monophyletic according to the one thousand transcriptomes project.
Bryophytes lack lignified vascular tissue and require wet conditions to survive.
Some mosses can survive in incredibly dry conditions and rehydrate later.
All bryophytes have gametophyte dominance in their life cycle.
Bryophytes need water to reproduce because their sperm have to travel through water.
Dawsonia superba is a moss that can grow up to two feet tall without lignified vascular tissue.
Hornworts are a group of bryophytes with a flat flap of tissue and little root-like structures called rhizoids.
Hornworts have a unique sporophyte that grows from a basal meristem, unlike most plants.
Liverworts can reproduce asexually by structures called gemmae.
Leafy liverworts have distinct ranks of upper and under leaves, unlike mosses.
Thyroid liverworts have a thallus with simple pores for gas exchange.
The life cycle of liverworts involves the production of archegoniophores and antheridiophores.
Gemmae in liverworts can grow into a clone of the gametophyte.
Spores in liverworts are produced by meiosis within the sporangium.
Spores in hornworts mature and are released from the top down as the sporangium dries out.
Bryophytes have a unique life cycle with distinct stages of gametophyte and sporophyte.
Transcripts
is the second video talking about bryophytes so overview of this video we're going to look at
lineages of bryophytes and we're only gonna look at two: we're going to look at Anthocerotophyta,
the hornworts, and Marchantiophyta, the liverworts. if you have maybe a not super recent
botany textbook even recent botany textbooks might refer to the liverworts as the Hepatophyta (which
hepato means liver) so that name was recently changed to the Marchantiophyta so our bryophytes
were the first group of plants to evolve on land we think and this says that they are paraphyletic
that's currently unknown the research that I've been using to kind of evolve our botany course
actually says that they are likely monophyletic which goes against pretty much anything else
you'll read and so that just means that they would have had a single bryophyte ancestor that then led
to their lineage where they you know you diversify from there and we get these different groups of
bryophytes whereas if they're paraphyletic we sort of get one group of bryophytes branching
off and we stay on this sort of path toward the rest of plants then another group of bryophytes
branches off so it's just about can we group them all and trace them all back to one shared common
ancestor that's only shared by that group or do they sort of share ancestors with other groups
along the way and it's looking like from this one thousand transcriptomes project that they might be
monophyletic so there's three major lineages all of them are small and prostrate and so there's
exceptions to this but that they lay kind of flat to the surface or aren't able to hold
themselves up right because they lack lignified vascular tissue so when we learned about xylem
we learned that it's made of sieve tube or not seep developments vessel elements and tricky 'its
and those are lignified cells with that secondary cell wall right fights don't have that so because
of this they require wet conditions to survive they don't have roots to penetrate down into
some kind soil surface there isn't a soil surface for them to penetrate down into right we just have
this rocky terrestrial surface when they first move so they're going to be reliant on you know
their fungal associates to help them scavenge water and maybe reliant on their cyanobacterial
associates to help them fix nitrogen as they have access to nutrients so they require wet
conditions there to survive I'm getting a little sidetrack here except a few mosses especially
there's large groups of mosses now that can survive and incredibly dry conditions that most
other organisms can't they have the ability to completely dry out and then stay in that condition
and then rehydrate later and live which most organisms can't do so mosses do have some kind
of exceptional abilities to be dry even though as a general rule bryophytes need water they
do need water to reproduce because their sperm have to travel through water to fertilize eggs
all of the bryophytes also have gametophyte dominance so when you look at a bryophyte you
see this green tissue it's the largest part of the organism it is haploid so all other plants when we
see this larger part of their lifecycle that's the green photosynthetic part that's a sporophyte but
for bryophytes it's the gametophyte so that this is a kind of trait that unites them together and
so the gametophyte is the larger part of the lifecycle it generally has a longer lifespan
and it's nutritionally independent so it's the photosynthetic part and can feed itself so there's
always exceptions this is Dawsonia superba it is a moss that can grow up to two feet tall it does
not have a lignified vascular tissue like we see in plants but it has this sort of analogous set of
structures where it has hydroids and leptoids where it's able to kind of transmit water and
sugars from its upper parts to its lower parts but it's not lignified let's look at this first
group of bryophytes are hornworts and current research that i'm using says that it's likely
that the hornworts are not genetically closest to vascular plants but perhaps they evolved first so
I'm just gonna cross that off because who knows right now it's all up for debate so what they look
like is this flat kind of flap of tissue that has little root-like structures so this whole
thing is the gametophyte these little root-like structures are called rhizoids so that just means
root like they don't function to absorb water they don't have any vascular tissue within them
they just function for anchorage so they are to kind of hook themselves to the terrestrial
surface and you do find fungal associates with these rhizoids so they sort of had this possibly
mycorrhizal relationship pre-roots that allowed them to maybe access any nutrients in that kind
of rocky surface and help break down that surface so this is our ballast and in this palace for
hornworts often you'll see little pockets where they have cyanobacteria living inside them so
again that's another association that would have allowed them to access nutrients in this
kind of harsh landscape and that's why we call them salad is because they're always this sort
of flat flap of undifferentiated tissue and on that thallus you have these little kind of vase
like structures and that's where the egg would have been produced inside this archegonium and
so the sporophyte grows out of the gametophyte so here's our sporophyte this is all diploid and
it is one big sporangium
and unlike most plants that we'll see there's only I think one other example of this that
we'll see during our body class this sporophyte grows from a basal meristem so we're used to
seeing apical meristems right the shoot apical meristem in the root apical meristem this tip
oriented growth where new cells would normally be produced at the tip however in this sport of
fight new cells are produced at the base and it pushes the rest of the sporophyte growth upward
so the oldest part of the sporophyte is up here who also interesting that the stomata and cuticle
are formed on the sporophyte but not necessarily on the gametophyte so we're going to start seeing
a lot of adaptations that are beneficial for living on land happening in the sporophyte
and that's actually going to lead us to this sporophyte dominance another feature that helps
you recognize hornworts if we're going to zoom in on this here so if we're looking at a horn we're
under the microscope its cells are gonna each have one large plastid with a pyrenoid those paranoids
are sort of ancestral features we see paranoids in our green algae like in our spirogyra and so
that is maybe pointing toward a more ancestral trait so here we see our alloyed liverworts are
not liverworts hornworts says the thallus it's this flap of undifferentiated tissue it's growing
a press to the surface prostrate and then it has the sporophytes growing up out of the gametophyte
so that's at match or trophy where the embryo is nourished in returning retained and then it's fed
through a system of cells here by the gametophyte and then here on the right we can see the mono
plastic condition where we have one large plastid inside each cell so that's pretty unique and it's
a good way to tell apart a thyroid liverwort from a thali one word here we see the hornwort
sporophytes that are maturing and releasing their spores so they start to D hiss from the top down
because this is where the most mature spores would be and they can dry out because they have stomata
all over them and the stomata allow the escape of moisture to dry out the sporangium once it's
dry and those spores have matured it will D hiss so it will split into these different segments
that kind of twist there's a little elaters in there these little kind of fibrils that help
disperse the spores and it does that from the tip downward from the most mature part to the least
mature our liverworts that I can look like either hornworts or mosses it makes them a little tricky
they can reproduce asexually by structures called gemmae and they have simple pores for
gas exchange so unlike the hornworts de ma or a hornwort sporophyte the head stomata which would
be regulated by guard cells liverworts are just going to have holes in the gametophyte that can't
open and close so they can't regulate their gas exchange and here it says most ancestral lineage
maybe not we don't know there's two different kind of body plans for a hornwort not for a liver work
sorry I've had to rerecord this like four times because PowerPoint keeps quitting on me so now
it's all just word salad okay so here's our leafy liverwort it has these kind of major ranks of
leaves the larger upper leaves are going to be produced in this sort of flat sheet and then if
you flip it over you'll have these ranks of little under leaves that are smaller and stick out of the
bottom and mosses don't have that so if you're trying to tell the difference between a leafy
liverwort and a moss you can look for those under leaves they're really small you can still see them
they'll produce rhizoids along this surface at any point they want to sort of attach to
that surface and they can produce the sporophytes either along the body or some species will produce
them just at the end of these structures so these are all sporophytes but now they're divided into
two main parts we have the seta which is the stock and we have the spur medium and that's
where meiosis happens and spores are produced that sporangium will generally dehisce to open
so when it dries out and split into these kind of four compartments and so that helps release the
spores and we will look at the thyroid liverworts and we draw the life cycle so here you can see
the leafy liverwort and these ranks of leaves so you have these larger upper leaves that would be
on the upper surface if we were this is flipped over under the microscope we could look at it the
other way and would look just like a moss except for a few key features but the underside because
these little tiny leaves so make sure to look for those this is a picture of what that looks
like in a hopefully less confusing way here is our thyroid liverwort and this is one that you might
see invading a nursery or greenhouse or anywhere where it's kind of like shaded cool conditions
where there may be growing shade tolerant plants this is a good invader and it invaded
the terrestrial surface so it's not surprising so over here on the upper right we can see an
archegoniophor so the archegonia would be produced under these little branches right there and then
the egg would be produced within the archegonium get fertilized and develop into a sporophyte which
we're seeing these really early sporophytes developing here they look like coconuts under
a palm tree and then the antheridiophore instead of being that tree like structure it looks more
like a flat plate and that's because water is going to bounce onto the antheridia and
splash the sperm out of those same three idea and hopefully onto in archegoniophore so here we see
those archegoniophores growing on a thallus and that thallus has all these little dots those are
simple pours and also if we look over here on the bottom right we might see these structures these
are those gemmae cups and they don't have very many gemmae in them anymore they've probably all
bounced out and been splashed out by water it's just a little disk of haploid tissue that's been
going to be a clone of the gametophyte that can land somewhere and grow into a new thallus so
we're going to draw the Marchantia lifecycle and label all the parts so meiosis is over
here random line is over there realistically I should leave myself more room on top but I did
not so here we go so let's start with some spores so we have spores are produced by meiosis they're
going to be genetically different from each other some of these might grow into a male gametophyte
that's going to produce antheridiophores
while others might grow into a female commute fight that's going to produce archegoniophores
and then both could produce gemmae
and those gemmae would then just grow into another gametophyte of the same type right so
gemmae from a male gametophyte would grow into another male gametophyte gemmae from a female
gametophyte would grow into another female gametophyte so we have the archegoniophore
so that just means the structure that bears the archegonia and here we have an antheridiophore
so the structure that bears the antheridia these are the gemmae cups oops gemmae cup with gemmae,
gemmae singular are gemma is called Gemma so here's our gametophyte we're going to
zoom in on the archegoniophore and the antheridiophore so if we look underneath
a branch of that archegoniophore there's going to be archegonia kind of nestled into the kind
of area where those branches come out inside that archegonium there'll be an egg to label this we
have the egg which was produced by mitosis and this structure here is the archegonium
and this is the neck or the venter of the archegonium if we zoom in on
the antheridiophore would see on the top of that structure up not I'm drawing this wrong
they're embedded in that surface let's start this again so we have this sort of disk like
structure that's at the top of the codon re-enter idea form that's the antheridial
head and kind of embedded in that are all of the antheridia so this is where sperm will be produced
so those little sperm are gonna get splashed off of the antheridial head and then travel
to an egg when we get the egg and the sperm meeting we get fertilization what you might
see in some of your textbooks or resources called syngamy that's when you're thinking
of karyogamy and fertilization both happening okay so fertilization this
happens on the female gametophyte in that archegonium so this is the archegoniophore
that's the archegonium and then now we have the zygote which forms on
that female gametophyte that zygote is going to grow by mitosis and it
does that growth on the female gametophyte so here's our archegoniophore and it has
sporangia with seta that grow underneath it so each of these purple structures is a sporophyte
and each one has seta it's that short little stock there and a sporangia and meiosis happens
within that sporangium to make spores here's a picture of some leafy liverworts for fights
they are very cute I love finding these they are pretty ephemeral they don't stick around
for long so here's some that get produced at the end of that gametophyte all right so here's our
seta (the stalk) and the sporangium at the top where the spores are produced so that's
the site of meiosis for all plants this site of meiosis is going to be inside that sporangium
so here we see they have opened by drying out and push themselves open that's dehiscence so
be hist to release their spores and this looks a lot like a moss right you might think it was
a moss but you'd have to take a close look at those leaves or look for these sporangia
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